A Borehole Acoustic Reflection Survey (“BARS”) is utilized to image near-wellbore structures in a subterranean formation penetrated by the wellbore. Such imaging utilizes waveform data acquired by an acoustic tool conveyed within the wellbore. Such acoustic tools comprise acoustic transmitters and receivers operable to acquire the waveform data. That is, acoustic signals transmitted from a transmitter reflect from boundaries and fractures of the formation before being detected by the azimuthally spaced receivers. The detected signals are processed to generate the waveform data indicative of physical and/or other parameters of the formation. The BARS data provides a two-dimensional image, in directions of the longitudinal axis of the wellbore and the distance between the wellbore axis and the near-wellbore features (“reflectors”) in the formation. The azimuthal location of each reflector is determined using differences between arrival times of the signals corresponding to the same reflector (“event signals”) at the azimuthally spaced receivers, based on the assumption that the wavefield excited by the reflected wave in the wellbore is a plane wave. Thus, the recorded event signals are expressed by time shifts, and the amplitudes and shapes of signals are identical for the azimuthally spaced receivers.
However, in actual BARS data acquired in real wellbores, event signals received by the different receivers exhibit apparent amplitude differences for P-waves and SV-waves. The apparent amplitude differences are inconsistent with the above-described assumption that the wavefield excited by the reflected wave in the wellbore can be regarded as a plane wave. Consequently, the azimuthal locations of reflectors determined utilizing this assumption are inaccurate.